/*      $OpenBSD: pipe.h,v 1.29 2022/07/09 12:48:21 visa Exp $  */

/*
 * Copyright (c) 1996 John S. Dyson
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    this list of conditions, and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Absolutely no warranty of function or purpose is made by the author
 *    John S. Dyson.
 * 4. This work was done expressly for inclusion into FreeBSD.  Other use
 *    is allowed if this notation is included.
 * 5. Modifications may be freely made to this file if the above conditions
 *    are met.
 */

#ifndef _SYS_PIPE_H_
#define _SYS_PIPE_H_

#ifndef _KERNEL
#include <sys/time.h>                   /* for struct timespec */
#endif /* _KERNEL */

#include <sys/event.h>                  /* for struct klist */
#include <sys/sigio.h>                  /* for struct sigio_ref */

/*
 * Pipe buffer size, keep moderate in value, pipes take kva space.
 */
#ifndef PIPE_SIZE
#define PIPE_SIZE       16384
#endif

#ifndef BIG_PIPE_SIZE
#define BIG_PIPE_SIZE   (64*1024)
#endif

/*
 * Pipe buffer information.
 * Separate in, out, cnt are used to simplify calculations.
 * Buffered write is active when the buffer.cnt field is set.
 */
struct pipebuf {
        u_int   cnt;            /* number of chars currently in buffer */
        u_int   in;             /* in pointer */
        u_int   out;            /* out pointer */
        u_int   size;           /* size of buffer */
        caddr_t buffer;         /* kva of buffer */
};

/*
 * Bits in pipe_state.
 */
#define PIPE_ASYNC      0x004   /* Async? I/O. */
#define PIPE_WANTR      0x008   /* Reader wants some characters. */
#define PIPE_WANTW      0x010   /* Writer wants space to put characters. */
#define PIPE_WANTD      0x020   /* Pipe is wanted to be run-down. */
#define PIPE_EOF        0x080   /* Pipe is in EOF condition. */
#define PIPE_LOCK       0x100   /* Thread has exclusive I/O access. */
#define PIPE_LWANT      0x200   /* Thread wants exclusive I/O access. */

struct pipe_pair;

/*
 * Per-pipe data structure.
 * Two of these are linked together to produce bi-directional pipes.
 *
 * Locking:
 *      I       immutable after creation
 *      S       sigio_lock
 *      p       pipe_lock
 */
struct pipe {
        struct  rwlock *pipe_lock;
        struct  pipebuf pipe_buffer;    /* [p] data storage */
        struct  klist pipe_klist;       /* [p] list of knotes */
        struct  timespec pipe_atime;    /* [p] time of last access */
        struct  timespec pipe_mtime;    /* [p] time of last modify */
        struct  timespec pipe_ctime;    /* [I] time of status change */
        struct  sigio_ref pipe_sigio;   /* [S] async I/O registration */
        struct  pipe *pipe_peer;        /* [p] link with other direction */
        struct  pipe_pair *pipe_pair;   /* [I] pipe storage */
        u_int   pipe_state;             /* [p] pipe status info */
        int     pipe_busy;              /* [p] # readers/writers */
};

#ifdef _KERNEL
void    pipe_init(void);
#endif /* _KERNEL */

#endif /* !_SYS_PIPE_H_ */